Microprocessors typically require a regulated voltage supply having a particular voltage level. FIG. 1 is a simplified block diagram of a system 100 having a microprocessor 110 and a voltage regulator 150 that provides a power supply voltage to the microprocessor.
Microprocessor 110 is an example of a processor having a voltage identification VID signal 112 that specifies the operating voltage of the processor. Voltage regulator 150 receives the VID signal 112 and outputs a supply voltage VCC 152 to processor 110. Voltage regulator 150 is connected to a input voltage VIN and a ground voltage VSS from which it produces the supply voltage VCC at the level specified by the VID signal.
Different types of processors can have different supply voltage requirements. Even different parts of the same processor can have different voltage requirements, such as a supply voltage required for a processor core and another voltage required for a level 2 cache. The supply voltage of a processor may be changed by a manufacturer for a variety of reasons, such as to optimize performance, increase production yields, and reduce power consumption.
In addition, it is desirable to design a single board, such as a motherboard, to accept many different processors. Thus, it is important that voltage regulators be designed to provide the voltage level specified by the VID signal 112 of the processor 110. See VRM 8.3 DC--DC Converter Design Guidelines, Order No. 243870-002, and Pentium.RTM. Processor Flexible Motherboard Design Guidelines, Order No. 243187, Intel Corp., Santa Clara, Calif. Voltage regulators have been developed that have a digitally programmable output voltage that can be controlled by the VID signal of a processor. See the LTC1553 5-bit Programmable Synchronous Switching Regulator Controller for Pentium II Processor, Linear Technology Corp., Milpitas, Calif., www.linear-tech.com.
In multiprocessor systems, each processor typically requires its own voltage regulator. Each voltage regulator provides the supply voltage specified by the VID signal of its corresponding processor. However, this increases the number of chips required in the multiprocessor design. Therefore, the need remains for a way to reduce the number of voltage regulators needed for a multiprocessor system.